1. Field of the Invention
Although the catalytic properties of microorganisms have been exploited in various biochemical processes for years, the techniques generally employed to carry out these transformations have their origins in traditional batchfermentation methods, and have undergone little change since their original initiation. With the relatively recent appearance of recombinant DNA techniques for genetically altering cellular function and metabolism, there is an increasing need to improve the exploitation of microorganisms to produce valuable products or process effluent streams. There is little known about the dynamics of cell growth. The ability to supply nutrients to the cell organisms, the manner in which the organisms become distributed in a reactor, the effect on such distribution of the supply of nutrients to the organisms and the removal of excretion products from the organisms remains a matter of uncertainty. In addition to the concerns about distribution of nutrients and removal of excretion products, the fragile nature of the cells limits the manner in which the cells may be handled during the processing. Techniques which have found application include fermenting involving mechanical agitation and a flowing stream through a reactor for supplying nutrient and removing product; air-lift fermentors; fluidized-bed fermentors; immobilized cells and the like.
In order to maximize the benefits of using microorganisms, substantial improvements are required in the yields of product obtained employing microorganisms where the yield is based on per unit of reactant as well as per unit volume of rector, the packing density of the microorganisms, the rate of production, the viability of the organisms, and the like.
2. Description of the Prior Art
U.S. Pat. No. 3,580,840 describes a method and apparatus using microorganisms for sewage treatment employing a porous membrane. U.S. Pat. No. 3,767,790 teaches microorganism entrapment for controlled release. See also U.S. Pat. No. 3,860,490. U.S. Pat. No. 3,875,008 teaches microorganism encapsulation in a hollow filament. U.S. Pat. No. 4,148,689 teaches entrapment of microorganisms in a gelled sol.